Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so mutation safety is covered. The description adds nothing beyond them on the things that actually matter for a financial calculator: contribution timing (annuity-due vs ordinary), whether annualRatePercent is compounded monthly, rounding/precision of the result, or whether the rate is nominal or effective. No output schema exists, so the description should have covered the return shape and does not.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The line is short and front-loaded, but it is under-specified rather than concise: it is essentially a title restatement plus an acronym gloss, with no sentence that carries operational content. Brevity here costs more than it saves.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a four-parameter financial calculator with no output schema and 25% schema coverage, the description should say what it returns (future value, invested principal, gain) and under which contribution convention. Neither is present, so the agent must guess at conventions that change the numeric result.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is only 25% — startDate is documented (including its label-only, non-monetary effect and the day-29-31 clamping), but the three required parameters are bare. The description supplies no meaning for monthlyInvestment, annualRatePercent, or years, and critically does not resolve the compounding convention that determines the answer.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description expands the opaque acronym (SIP = systematic investment plan) and names the output (future value), which is genuinely informative given the name alone. But it is a noun-phrase label with no verb and no differentiation from siblings like calculate_compound_interest or calculate_loan, which compute economically similar things.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no statement of when to use this versus any alternative, no prerequisites, and no exclusions. An agent choosing between calculate_sip, calculate_compound_interest, and calculate_loan gets no routing help from this text.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.